Small, high performance gas turbine engines typically have large disk shaped components which rotate at a high rate of speed. For example, turbine and compressor wheels may rotate up to 50,000 RPM. Dynamic unbalance of such components leads to severe vibration which reduces the useful life of not only the components but also of the surrounding support structure.
The present method of spin balancing metallic compressor and turbine wheels involve selective removal of material from a portion of the central disk area in order to equalize, as much as possible, the rotating mass, and therefore the centrifugal forces, on diametrically opposite portions of the wheel.
However, with the recent development of high temperature ceramic turbine wheels, such methods are no longer satisfactory. Such advanced turbine wheels are being developed using silicon nitride, silicon carbide, and silicon carbide coated carbon-carbon composites which are all very brittle and sensitive to surface cracks. Therefore, any balancing method must avoid the formation of strength limiting cracks, especially in the critical central disk area. In addition, the thin coatings on composite disks cannot be ground away without loss of the coating's primary function of oxidation protection.
In view of the foregoing, it should be apparent that there is an unmet need in this art for improvements in the dynamic balancing of ceramic turbine components.
It is therefore an object of the present invention to provide a simple and inexpensive method to spin balance ceramic turbine wheels without removal of critical structural material.